Exam 200-301 topic 1 question 266 discussion

Actual exam question from Cisco's 200-301

Question #: 266
Topic #: 1

[All 200-301 Questions]

Refer to the exhibit. Which action do the switches take on the trunk link?

A. The trunk does not form, and the ports go into an err-disabled status.
B. The trunk forms, but the mismatched native VLANs are merged into a single broadcast domain.
C. The trunk forms, but VLAN 99 and VLAN 999 are in a shutdown state.
D. The trunk does not form, but VLAN 99 and VLAN 999 are allowed to traverse the link.

Show Suggested Answer

Suggested Answer: B 🗳️

by nenotronix at March 10, 2021, 6:43 a.m.

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splashy

Highly Voted 2 years, 11 months ago

Every time i see this question... i hate it more. B is indeed the "least incorrect/bad" option but it's just a ridiculously small part of the whole answer. Meaning this would be the end result WITHOUT spanning tree existing and putting the end of the trunk that was last configured (mismatched) in a "broken status" blocking all untagged traffic on that port. Call me crazy but i hate questions where i need to envision a parallel reality where spanning tree does not yet exist.

upvoted 23 times

RougePotatoe

2 years, 9 months ago

To explain if anyone do not understand his complaint. According to Cisco STP is enabled by default on all cisco switches. Cisco documentation says STP should shut down ports when there is a native vlan mismatch. Although, I have yet to see this happen on Packet Tracer or in Lab equipment.

upvoted 18 times

GhostWolf

2 years, 9 months ago

Thanks.

upvoted 1 times

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Rado_Piatek

Most Recent 4 weeks ago

Selected Answer: B

Trunk forms, and the untagged frames will be interpreted with native vlan number, so the C cannot be the answer.

upvoted 1 times

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ssbipa6

7 months, 1 week ago

You would understand if you have configured native vlan mismatch like on GNS3 or EVE-NG. you only receive warnings, but does not shut down any trunk port. So B is the answer.

upvoted 1 times

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xtraMiles

1 year ago

Another one of these. I'll keep coming back to the same link whenever I see this native VLAN mismatch. https://learningnetwork.cisco.com/s/article/effects-of-mismatched-native-vlans-on-a-trunk-link I guess I'm just going to have to interchangeably use the words restricted, shut down, and broken. I'm picking C here because of the link, but if it's B that Cisco Exam wants, then I'll pick that for the exam.

upvoted 2 times

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allyou

1 year, 3 months ago

Selected Answer: C

C is correct https://learningnetwork.cisco.com/s/article/effects-of-mismatched-native-vlans-on-a-trunk-link#:~:text=at%20receiving%20switch-,Situation%201,-The%20native%20VLAN

upvoted 1 times

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41a9d4b

1 year, 6 months ago

As I understood: If the Native VLAN is not the same on both ends of the link, a trunk will NOT dynamically form. If the trunk is formed through trunk mode (as it is here), and there is a native vlan missmatch, than the trunk will be formed but the vlans are merged to a single broadcast domain.

upvoted 3 times

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